A survey of surface tension,molar volume and density for Sn–Ag–Cu–Bi–Sb quinary alloys as lead-free solders

ABSTRACT

By applying the geometric models and the theoretical equation, the surface tension, the molar volume and the density were studied. The empirical calculations were carried out in temperature range 623?K?≤?T?≤?1123?K. Only few thermophysical properties were estimated for eight quinary alloys: Sn3.55Ag0.5Cu3Bi3Sb, Sn3.48Ag0.5Cu3Bi5Sb, Sn3.48 Ag0.5Cu5Bi3Sb, Sn3.40 Ag0.5Cu5Bi5Sb, Sn3.53Ag1Cu3Bi3Sb, Sn3.46Ag1Cu3Bi5Sb, Sn3.46Ag1Cu5Bi3Sb, Sn3.38Ag1Cu5Bi5Sb. The results show that surface tension and density have a linear appearance for all temperatures. We have also studied the influence of the composition and temperature in the studied alloys. The obtained theoretical results are compared with the experimental ones and with the conventional Pb–Sn welds.     

Hall-Effekt abschreckend kondensierter Schichten des Systems Zinn-Kupfer

Tin alloys with different contents of copper between 0 and 100 atomic-% are produced by simultaneous condensation of the two components onto a cooled substrate. The electrical resistance, the transition temperature of superconductivity, and the Hall coefficient of the films are measured immediately after condensation, during annealing to about 350? K, and recooling to helium temperatures. The observed properties of such alloys differ considerably from those of bulk material. A rather high transition temperature of about 7? K is observed for copper contents of more than 8 atomic-%. The high transition temperature disappears in connection with cristallisation of the tin component during annealing. Simultaneously with this change of the transition temperature a sharp decrease of the negative Hall coefficient occurs. The results are discussed with regard to a possible influence of the hole concentration on the superconductivity of tin.     

Über die charakteristische TemperaturΘ R abschreckend kondensierter Metallschichten

A cryostat is described which allows to reach any temperature between 10 and 320° K in less than 4 min and to maintain it within ±0·1° K. The resistance of quenchingly condensated Cu, Pb, Sn, In, and Hg films is investigated. During isochronal annealing the high residual resistance after condensation decreases irreversibly, i.e. the mean free path of the electrons increases. By the annihilation of the lattice defects also the slope of the temperature dependent resistance is altered. This behaviour can be explained with the Bloch-Grüneisen theory by lowered characteristic temperaturesΘ _R, which approach after annealing at higher temperatures the values of the bulk metals. The known shifts of the transition temperature of superconducting films after condensation are interpreted by these loweredΘ _R-values, which are caused by volume increase, and the small mean free path of the normal electrons.     

Supraleitung von Lanthan-Folien und von aufgedampften Lanthan-Schichten mit Zusatz von Gadolinium

Foils of lanthanum were found to be converted entirely to the h. c. p. modification by the rolling process. This made it possible to obtain the superconducting transition temperatures for both the h. c. p. and f. c. c. modifications of lanthanum from measurements of the electrical resistivity. Lanthanum foils in the h. c. p. form exhibited a superconducting transition at 4.9° K while foils in the f. c. c. form became superconducting at 6.0° K. Cold working lowered the transition temperature of the h. c. p. modification. — Quenching condensation provided films of the h. c. p. modification, their transition temperature being depressed by the quenching condensation. — Small additions of gadolinium lowered the transition temperatures as well of the quenchingly condensed as of the annealed films at the same rate of 4.5° K per at % Gd. From the accordance of these rates it is concluded that the lowering of the transition temperature by paramagnetic impurities is not affected by quenching condensation. The results of the measurements on La-Gd films are also in accord with those ofMatthias et al. obtained on bulk specimens.     

Der Einfluß der Unterlage auf die Struktur und Leitfähigkeit metallischer Aufdampfschichten

The influence of the substrate on the electrical conductance and on the structure of condensed metal films is investigated. Ag, Cu and Sn films are condensed at different temperatures onto two identical quartz plates. One of them was prenucleated at room temperature. At low condensation temperatures the influence of the metallic prenucleation on the structure of the film is very strong. Surprisingly we find the same influence if the prenucleation and the film are of the same metal. The influence of the nucleation on the electrical conductance of the film is not so strong. Gold films are condensed onto different dielectric substrates at room temperature. From measurements of the electrical conductivity we find that a fraction of the conduction electrons are specularly reflected at the boundaries of the film. This fraction depends on the substrate material and the annealing temperature of the film.     

Lichtelektrische Messungen an stark gestörten Zinn-, Blei- und Cadmiumschichten

Thin films of Sn, Pb and Cd are produced by quenching condensation at low temperatures. The photoelectric emission and the electrical resistivity are measured after condensation and during annealing. In the case of Sn and Pb both the electrical resistance and the photoelectric sensitivity decrease during annealing. The resistance of Cd-films shows the same behaviour, but the photoelectric sensitivity is lowered only above 90 °K.     

Schichten aus amorphem Eisen

Thin films of iron are condensed onto a substrate at 20 ?K. After condensation and during annealing the electrical resistance is measured and Debye-Scherrer-diagramms are taken. The structure of the films depends on the evaporation rate and the vacuum conditions during condensation. In a good vacuum (10^?6 Torr) and for a high evaporation rate (100 å/sec) the films grow crystalline. Greater residual gas pressures and a slow evaporation rate (5 å/sec) lead to amorphous films. The amorphous structure is supposed to be induced by residual oxygen. A method is described to produce amorphous films of iron also in a high vacuum by condensing simultaneously small additions of Fe-oxide, Fe-selenide, Fe-sulfide, Si or Ge on a substrate at 20 ?K. During annealing the amorphous films change into the body-centered cubic structure of α-iron within a narrow range of temperature. Si is found to be the most effective substance to prevent crystallisation. Admixtures of Cu, Ag, Pb or SiO only lead to a state of high disorder, they do not prevent crystallisation of the Fe-films at any temperature of condensation.     

Zum magnetischen Nachweis der Supraleitung aufgedampfter Metallschichten

There is described an apparatus for the statement of superconductivity and ferromagnetism of a single evaporated film in the temperature range from 1.8° to 300° K. The observation of the magnetic moment of the film in a homogeneous alternating magnetic field is made possible by means of a special device of two sense coils. Tests with Pb and Sn foils result in the known transition temperatures of bulk material. A Sn film in a highly disordered state is produced by quenching condensation. The magnetic transition of such a film is found to be 0.8° K higher than the transition temperature of the annealed film. The result agrees with the resistance measurements by W.Buckel and R.Hilsch. The magnetic measurement proves the increased transition temperature for the whole material of the film.     

Electrical resistivity of Sn–3.5Ag–xBi solder melts

This article reported the temperature dependence of the electrical resistivity (ρ) of liquid Sn–3.5Ag lead-free solder alloy in continuous heating and cooling processes with varying Bi content in the range of 0, 2, 3.5, 5, and 7?wt.% Abnormal transitions can be observed on ρ–T curves, which indicate liquid–liquid structure transition (LLST) occurs in Sn–3.5Ag–xBi melts. Interestingly, unlike the pattern at first heating cycle, the LLST is reversible during subsequent cooling and heating cycles. Sn may play an important role on the reversibility, and Bi has a noticeable influence on the turning temperatures and characteristics during first heating cycle. The transition mechanism is analyzed from the viewpoint of short-range orders.     

Die Übergangstemperatur der Supraleitung verschiedener Metalle unter dem Einfluß sehr dünner Oxydschichten

The superconducting transition of thin films of Al, In, Tl, Pb, Sn, and Ga⁺ is investigated by resistance measurements before and after the low temperature oxidation of the surface. The films are condensed onto a crystalline quartz plate to a thickness of about 100 Å or less at a temperature of mostly 105 °K. The oxidation process below 40 °K was described in a previous paper. After a theory ofMott, it may be understood by the tunneling of electrons from the metal to some acceptor levels of the oxygen molecules at the outside of the oxide layer. This way, a strong electric field arises which, on the one hand, facilitates the motion of metal ions outwards to form oxide molecules and, on the other hand, is suspected to affect the transition temperature. The experimental results show a shift of the transition to higher temperatures with the metals Al, In, and Tl, however, with the metals Sn, Pb, and Ga⁺ to lower temperatures. These results agree qualitatively very well with direct measurements of the influence of surface charges on the superconducting transition of Sn and In byGlover andSherrill. TheT _c -shift depends clearly upon the film thickness and amounts to about 0.3 to 0.4 °K for the thinnest films used. Some experiments are undertaken in order to prove the existence of the electric field. Removing the residual oxygen molecules on top of the oxide layer destroys the acceptor levels and causes a reduction of the transition temperature to the value observed with the oxygen free film. As expected, the thickness of the oxide layer is not important for the magnitude of theT _c shift.     

Metal-insulator transition and superconductivity in SnAr films

We studied the conductivity and superconducting transition temperature T_c of SnAr films. The films were prepared by condensing the SnAr mixture on a sapphire substrate held at 5 K. A plot of the conductivity as a function of Sn concentration shows a metal-insulator transition which agrees with a percolation model consisting of Sn clusters embedded in solid Ar. A drop of T_c is observed below the percolation threshold.     

Zur Erzeugung amorpher Zinn-Schichten durch abschreckende Kondensation mit Fremdzusätzen

Thin films of Sn with additives are prepared by quench condensation. The annealing behaviour of the electrical resistivity and the transition to the superconducting state of these films are investigated in relation to the dependence of composition and film thickness. The data indicate, whether the films are in an amorphous state or not. It appears that the films become amorphous, if the addition has an atomic radius less than Sn and if the mean valence electron concentration is less than 3.7. With further reduction of the valence electron concentration the amorphous films become more stable and the temperature of transformation from the amorphous state to the crystalline state rises. The thickness dependence of the transformation temperature can be explained with a simple further assumption.     

Conducting properties of In2O3:Sn thin films at low temperatures

Electrical conductivity, Hall effect and magnetoresistance of In₂O₃:Sn thin films deposited on a glass substrates at different temperatures and oxygen pressures, have been investigated in the temperature range 4.2–300 K. The observed temperature dependences of resistivity for films deposited at 230 °C as well as at nominally room temperatures were typical for metallic transport of electrons except temperature dependence of resistivity of the In₂O₃:Sn film deposited in the oxygen deficient atmosphere. The electrical measurements were accompanied by AFM and SEM studies of structural properties, as well as by XPS analysis. It is established that changes of morphology and crystallinity of ITO films modify the low-temperature behavior of resistivity, which still remains typical for metallic transport. This is not the case for the oxygen deficient ITO layer. XPS analysis shows that grown in situ oxygen deficient ITO films have enhanced DOS between the Fermi level and the valence band edge. The extra localized states behave as acceptors leading to a compensation of n-type ITO. That can explain lower n-type conductivity in this material crossing over to a Mott-type hopping at low temperatures. Results for the low temperature measurements of stoichiometric ITO layers indicate that they do not show any trace of metal-to-insulator transition even at 4.2 K. We conclude that, although ITO is considered as a highly doped wide-band gap semiconductor, its low-temperature properties are very different from those of conventional highly doped semiconductors.     

Superconductivity of A1-type SnSb,SbTe and TeI alloys

Superconducting A1-type Sn, SnSb, Sb, SbTe, Te, Te I and I films were vapour-quenched on glass substrates quench-coated with CaO. The highest transition temperature is exhibited by 100 Å thick 20Sn–80Sb films, which become superconducting at 21.6 K.     

Elastic properties of amorphous water at low temperatures

We have studied the elastic properties of thin films of amorphous water (a-H₂O), prepared at 4.4 K by quench condensation. At low temperatures acoustic anomalies are observed, which are characteristic for amorphous solids. Annealing, even at moderate temperatures, reduces the number of tunneling states. A strong increase of the acoustic absorption is observed in the vicinity of the annealing temperatures. This indicates that structural rearrangements are possible in quenched condensed films at temperatures well below the glass transition.     

Ag−Sn Alloys and dental amalgams: A119Sn Mössbauer,x-ray diffraction and scanning electron microscopy study

Examination has been made on aged and fresh Ag?Sn alloys and on commercial Cu?Ag?Sn dental alloys. Although x-ray diffractograms of aged Ag?Sn showed only λ Ag?Sn and free silver,¹¹⁹Sn Mössbauer spectra exhibited Sn(IV) oxide also. A low Debye temperature showed the oxide to be in intimate dynamical contact with the metallic matrix. Upon adding mercury, the phases λ₁ Ag?Hg and η′ Cu?Sn were observed in a commercial specimen. Conversion-electron spectra of a mercury-coated disk showed the presence of λ₂ Sn?Hg and a distribution of line positions smaller than that for particulate amalgams. Internal oxidation was found to prevent amalgamation.     

Zur Theorie der Übergangstemperaturen von supraleitenden Doppelschichten (Proximity-Effekt)

A theory of the transition temperature of superconducting, superposed films is given by generalizing the methods ofde Gennes andWerthamer. It is shown that the transition temperature of nonhomogeneous superconductors obeys a general rule, which is formally of the same kind as the corresponding formula for homogeneous superconductors and is valid for all mean free paths. The results ofWerthamer follow analytically in the dirty limit if the transition temperatures of the superposed films are nearly equal, but there is numerical agreement for almost all superconductor-superconductor films. In the thin film limit and for normalconductor-superconductor films there are essential deviations. The theory is in good accord with the experimental data. By calculating the unknown interaction constant of copper from the experimental transition temperatures of superposed Cu-Pb films one gets for copper a transition temperature of the order of 10^?2°K.     

Interdiffusion in two-layer Pd/Ag films II. “Cold” homogenization mechanisms

Interdiffusion processes in thin epitaxial polycrystalline Pd/Ag films in the temperature range 20–500°C are studied by transmission electron microscopy, electron diffraction and electrical resistance methods. Homogenization is investigated both during condensation and under conditions of postcondensation annealing.The basic processes of homogenization associated with GB diffusion along migrating boundaries. It is found that in real polycrystal films with wide spectrum of grain sizes few mechanisms can occur simultaneously or subsequently: recrystallization induced diffusion, diffusion induced grain boundary migration, activation of bulk diffusion in fine grain clusters, bulk diffusion through interphase boundary. The conditions for prevailing one of them can be provided by changing condensation and postcondensation annealing temperatures or by choosing certain grain size.     

Einfluß adsorbierter Gase auf Supraleitung und elektrische Leitfähigkeit dünner Thalliumschichten

Some effects of adsorbed gases on superconductivity and normal electrical conductivity of thallium films have been investigated. These films were 50 to 700 Å thick and were produced by condensation of thallium vapor on a crystalline quartz, plate at about 100 °K. At 3 °K adsorbed oxygen lowers the transition temperature and slightly increases the residual resistance. Heating of the film results in a steep increase of resistivity at about 15 °K and shifts the transition temperature to a considerably higher value. The changes in electrical conductivity and transition temperature increase with decreasing film thickness. With the thinnest films, the resistivity increases up to 50 per cent. The maximum shift of the transition temperature is 0·3 degrees. From the resistivity behavior, it can be inferred that the adsorbed oxygen molecules accept conduction electrons at 15 °K, thus changing the kind of their bond. This shows up in a decrease of the effective film thickness by 5 to 10 Å. Further, results of adsorption experiments with hydrogen, nitrogen and argon are reported. These results depend to a great extent on the purity of the gases.     

Zur Oxydation von Metallen bei sehr tiefen Temperaturen

The formation of oxide films on various metals has been investigated in the temperature range between 1·5 and 100°K. The metal films (50 to 150Å thick) were produced by condensation of the vapor on a quartz plate at about 100°K. After cooling down the films to helium temperatures, oxygen molecules were condensed to the fresh metal surface. The electrical resistance was measured before, during and after this O₂ condensation at temperatures between 1·5 and 300°K. The formation of an oxide layer causes an increase of the electrical resistance, since the conductivity of the oxide is comparatively low. The resistance behaviour of the metals investigated indicates two different steps of oxidation each one starting at a certain “characteristic” temperature below 25°K. Below the lower characteristic temperature, no reaction takes place. Increasing the temperature slowly, the oxide layer grows up to a final thickness. No further growing is detectable between 50 and 150°K for most of the metals. The results are discussed with regard to theoretical considerations ofMott, Cabrera andHauffe.